Chronic kidney disease (CKD) is classified into five stages (CKD stages):
| Stage | GFR (ml/min per 1.73 m²) | Positive protein detection in urine | Neg. protein detection in urine |
| 1 | ≥ 90 | Renal disease with normal GFR | Normal findings |
| 2 | 60-89 | Renal disease with mildly impaired GFR (mild renal function impairment). | Mild renal function impairment but no renal disease |
| 3 | 30-59 | Renal disease with moderately impaired GFR (moderate insufficiency). | Renal disease with moderate renal function impairment |
| 4 | 15-29 | Renal disease with severely impaired GFR (high-grade insufficiency). | Renal disease with severe renal function impairment |
| 5 | <15 (or dialysis requirement) | Chronic renal failure (end-stage renal disease). | Chronic renal failure (terminal renal failure) |
The glomerular filtration rate (GFR) indicates how well the so-called urinary substances uric acid, urea and creatinine are excreted. This value is the best way to identify kidney damage. The normal value is 95-110 ml/min per 1.73 m². Urinary means that the substances must normally be excreted in the urine, otherwise they would lead to symptoms of poisoning.Chronic renal insufficiency is increasingly classified as follows.
| Stage | eGFR* (ml/min per 1.73 m²) | Traditional designation |
| CNI 1 | ≥ 90 | Kidney damage |
| CNI 2 | 89-60 | Renal insufficiency |
| CNI 3a | 59-45 | Compensated retention |
| CNI 3b | 30-44 | Compensated retention |
| CNI 4 | 29-15 | Decompensated retention |
| CNI 5 | < 15 | Terminal renal failure with or without hemodialysis therapy (HD). |
* eGFR stands for: estimated GFR (estimated glomerular filtration rate): calculated glomerular filtration rate according to standard formulas (e.g., Crockoft-Gault, MDRD, CKD-EPI).
Prognostic assessment of chronic renal failure.
| Albuminuria (mg/l) | ||||||
| A1 | A2 | A3 | ||||
| Normal to slightly elevated | Moderately elevated | Highly elevated | ||||
| < 30 | 30-300 | > 300 | ||||
| Glomerular filtration rate (ml/min per 1.73 m²) | G1 | Normal to high | ≥ 90 | |||
| G2 | Slightly lowered | 60-89 | ||||
| G3a | Slightly to moderately decreased | 45-59 | ||||
| G3b | Moderately to severely decreased | 30-44 | ||||
| G4 | Strongly degraded | 15-29 | ||||
| G5 | Renal failure (ESRD) | < 15 | ||||
Risk of progression of kidney disease, as well as the occurrence of complications:
| Low | |
| Moderate | |
| High | |
| Very high |
